In general, if glass windows installed on wall surfaces of a building are allowed to stand for a long period of time, they are easily contaminated by being influenced by external dust, environmental pollution, rainwater, and the like, and thus become dirty. For this reason, the windows installed on the outer wall of the building are required to be frequently washed in a proper cycle in order to maintain a daylighting property and an aesthetic sense. However, in such a window washing work, the inner surface of the window where a person's hands reach can be cleaned relatively easily using rags or the like. On the other hand, since the outer surface of the window where a person's hands do not reach well is very inconvenient and difficult to clean, the dirty window is generally left to stand. In particular, in case of the veranda window of high-rise apartments, it is required that a person should wash the window while watching the outside view with him or her sticking his or her head out of the window in order to watch the outer surface of the window. Thus, conventionally, there occurs a problem in that the cleaning of the window is inconvenient and involves a considerable risk in terms of safety. In an attempt to solve the problem, there have been developed various window cleaning devices which can wash the window more conveniently and safely.
Among these window cleaning devices, the window cleaning devices which are currently used most conveniently are so-called magnet type double-sided window cleaning devices that allows a user to clean both surfaces of a glass window at the inner side of a building. Such a conventional double-sided glass window cleaning device has a slight difference in the detailed structure depending on each product, but is basically configured such that a pair of cleaning units having a built-in magnet are disposed on the indoor and outdoor side surfaces of the window so that a user moves the indoor side window cleaning unit along the surface of the window to wash the window with him or her griping it in a state in which the cleaning units are attached to each other, and thus the washing operation can be performed on the outdoor and indoor side surface of the glass window simultaneously.
The window cleaning device that is configured to simultaneously clean the indoor side surface or both surfaces of the window using the magnet has currently been developed in various forms. Such a magnet type glass window cleaning device can easily found in a plurality of documents including Korean Patent Registration No. 550279, Korean Patent Laid-Out Publication No. 10-2006-0085274, and Korean Utility Model Registration No. 0305524.
Such a conventional magnet type window cleaning device has an advantage in that a user can clean the outdoor side surface of a window even without going out but still entails problems in that since the user moves the cleaning device by applying a force to a body unit with him or her gripping a handle personally to clean the window, he or she suffers from an inconvenience in use, and in that if the user does not apply a force in parallel with the glass surface to move the cleaning device, the outdoor side cleaning unit frequently falls down from the window. In addition, the conventional magnet type window cleaning device has disadvantages in that since the cleaning device is moved along the surface of the window only once to clean the window, old dirt stuck to the window is difficult to clean clearly, and in that in the case where a window is positioned at a high position where a user does not reach, he or she suffers from an inconvenience of having to climb up to the window using a ladder or a chair to clean the window.
Accordingly, the present inventor has developed an automatic window cleaning robot that can perform a cleaning operation while automatically moving on the surface of the window in an attempt to improve the problems associated with the conventional magnet type window cleaning device. The automatic window cleaning robot has been registered as Korean Patent Registration Nos. 10-1003486 and 10-0987121. The window cleaning robot according to the previously registered invention includes indoor and outdoor side robot units employing a drive wheel having a built-in magnet or magnetic material and uses a magnetic attraction between the drive wheels as a normal force necessary for the friction drive so that the robot units automatically perform a cleaning operation while being moved in a state of coming into close contact with the surfaces of the window. According to the previously registered invention as described above, there is provided a mechanism that can be automatically moved by the drive wheel even on the surface of the window, which is perpendicular to the ground surface so that an inconvenience involved in the conventional cleaning device is resolved in which a user must move the cleaning device with him or her gripping it personally to clean the window, and thus a window cleaning operation can be performed effectively.
Meanwhile, according to the automatic window cleaning robot as described above, since the outdoor side robot unit performing a cleaning operation is moved together with the indoor side robot unit by being attracted by the indoor side robot unit, a large capacity power supply is not needed but the automatic window cleaning robot preferably includes a built-in power supply needed to additionally drive a detergent supply pump or a sensor.
As a power supply for the outdoor side robot unit, a rechargeable battery can be contemplated which is built in the outdoor side robot unit and is re-charged for use after being operated for a predetermined time period. However, according to the aforementioned method, a user must check a battery charge state of the outdoor side robot unit at any time to recharge the rechargeable battery periodically. In this case, it is required that the entire drive of the robot should be stopped and the indoor and outdoor side robot units be separated from the window to recharge the battery, and then should be disposed on the surface of the window. Thus, there occurs a problem in that the user suffers from an inconvenience in use. In addition, the outdoor side robot unit has a separate battery built therein, thereby leading to an increase in the total weight of the outdoor side robot unit, and thus adversely affecting driving performance and safety of the robot unit. Further, there are many disadvantages in that a battery as a consumable having a limited lifespan must be purchased additionally and is required to be maintained.